A SPRING SYSTEM FOR RESILIENT SUSPENSION OF OBJECTS, SUCH AS VEHICLE SEATS

Abstract: The invention refers to a spring system for resilient suspension of objects subjected to great disturbing forces with low frequencies, such as vehicle seats and particularly driver's seats in railway vehicles, and for accommodation of movements with at least three degrees of freedom between object and base, the object (1) by means of two sets of guide means (2, 4) arranged vertically above each other being mounted freely movable substantially horizontally in two directions (x, y) at right angles to each other. In order to provide for a more compact and less complicated spring arrangement as well as in order to obtain a desirable progressive spring action, the invention suggests that the object (1) is permanently subjected to the force of a tension spring means (8), which at one of its ends is secured to the centre (7) of the horizontal underside of the object (1), supported by the upper set of guide means (2), and at its other end (9) is secured to the centre of the lower set of guide means (4), supported by the base, possibly at a downwards offset position.

Description: A spring system for resilient suspension of objects, such as vehicle seats. The present invention refers to a spring system for resilient suspension of objects subjected to great disturbing forces with low frequencies, such as vehicle seats and parti- cularly driver's seats in railway vehicles, and for accomoda- tion of movements with at least three degrees of freedom bet¬ ween object and base, the object by means of two sets of guide means arranged vertically above each other being moun¬ ted freely movable substantially horisontally in two direc- tions at right angles to each other. A spring system of this type is known from EP 0 054 880 as well as from the Swedish patent specification 66594 from the year 1926. In both cases, pairs of tension springs are used for controlling the movement in two directions at right angles to each other. The plurality of spring means makes this structure rather complicated. Spring systems of the most various kinds have been suggested during the years in order to solve different spring suspension problems, particularly in connection with vehic- les. Most often said spring systems have been focused on solving the spring problems in connection with vibratory motions of higher frequencies while the low frequencies close to 1 Hz have been paid little attention to. In the last years the health hazards in connection with the practising of various professions have been more observed and the attention has been more and more focused on such low-frequency vibrations which occur in certain types of vehicles and which imply great loads on the human body which might lead to occupational injuries. One such occupational category is for instance locomotive drivers, particularly drivers of heavy freight trains where movements in y-direc- tion (i.e. transversely to the direction of travel) might imply throw movements of a magnitude of up to 60 mm at rail- way failures. The accomodation of such movements requires spring suspensions with long stroke and in the last years suggestions have been made in order to improve the travel comfort to locomotive drivers without, however, any decisive success having been achieved. The object of the present invention is to suggest a device in spring systems of the afore-mentioned kind which has turned out to be a very good solution to the problems present. The invention is substantially distinguished in that the object is permanently subjected to the force of a tension spring means, which at one of its ends is secured to the centre of the horisontal underside of the object, supported by the upper set of guide means, and at its other end is secured to the centre of the lower set of guide means, sup- ported by the base, possibly at a downwards off-set position. The present invention now allows the provision of a really comfortable travel to the person sitting in the seat, which has been confirmed by theoretical as well as practical tests. By way of example the invention will be further des¬ cribed below with reference to the accompanying drawing, in which Fig. 1 is a perspective view of the inventive spring system, Fig. 2 is a side elevational view of the same system, Fig. 3 is a further side elevational view of the system at right angles to the view of Fig. 2 and Fig. 4 is a diagram illustrating the advantageous effects of the inventive system with respect to the total comfort improvement and the impact damping action in x, y and z direction. In Figs. 1-3 of the drawing an inventive spring system is illustrated, which comprises a substantially hori¬ sontal mounting plate 1, adapted to support an object subjec¬ ted to disturbing forces such as a vehicle seat and particu¬ larly a driver's seat in a non-illustrated railway vehicle. By means of a first set of guide means 2 the mounting plate is journalled freely movable in a first direction which has been indicated by an arrow x on the drawing. Said guide means might be of any known type but are most advantageously made as so-called linear bearings with ball bushings 2a. A bearing rod 2b runs therein and the number of linear bearings in the set amounts to at least two. The ball bushings 2a in their turn are mounted on an underlying and also substantially horisontal intermediary plate 3, which in its turn by means of a second set of guide means 4 is journalled freely movable in a direction at right angles to the first-mentioned direction, such as indicated by the arrow y on the drawing. Preferably, also said second set of guide means 4, which also are at least two in number, are of the same kind as the first set and hence consist of linear bearings with ball bushings 4a, which are slidably movable on bearing rods 4b. The arrangement is such that the ball bushings 4a preferably are mounted at the lower side of the intermediate plate 3 and run on the parallell bearing rods 4b, which in their turn are mounted on a substantially hori¬ sontal base plate 5. This is supported from a floor 6 or a corresponding base in e.g. a locomotive. According to the invention, from a position 7, prefe- rably at the centre of the lower side of the uppermost moun¬ ting plate 1 a tension spring means 8 extends, which in the drawing only has been indicated by means of broken lines, to a position at the centre of the lower set of guide means 4, supported by the base 6, and particularly at a position 9 vertically downwardly off-set in relation to said guide means 4. The tension spring means 8 thus always tends to keep its two mounting ends 7 and 9 located on the same vertical axis. Every disturbing active force in the x direction or y direc¬ tion which leads to a sliding movement of the mounting plate 1 and/or the intermediate plate 3 in x direction and y direc¬ tion, respectively or to a combined orbital motion, a so-cal¬ led yaw motion, in the horisontal plane will cause an exten¬ sion of the spring means 8 and hence the occurance of a cor¬ responding returning force. It is to be noted that the struc- tural arrangement according to the invention provides such a geometry of the motion of the tension spring 8 that the spring action will be progressive in a very advantageous way. The tension spring 8 can be of any known type but is preferably a gas hydraulic spring of elongated cylindrical type such as often is used within the vehicle field. Said gas-hydraulic spring may also be provided with a damping action, preferably adjustable, as is well known. As is evident from Fig. 3 the lower mounting end 9 of the tension spring 8 preferably is secured to a yoke 10 which extends downwardly from the lower side of the base plate 5, namely in order to assure a required spacing between the mounting ends 7 and 9 of the spring in view of the structure length of the tension spring 8, particularly when the same is a gas-hydraulic spring. The mounting end 9 lies on the verti¬ cal central axis of the base plate 5. The above-stated design allows that the mounting plate 1 and hence a driver's seat of e.g. a railway locomo¬ tive might be supported with a possibility for movements with three degrees of freedom, thus x, y and yaw. In spite of the relatively restricted space in driver's compartments of loco¬ motives and the like the required long spring travel distan- ces of up to 80 mm might be provided owing to the spring system suggested according to the invention. This provides for the achievement of a substantially improved travel com¬ fort to the person sitting in the driver's seat. This is evident from practical tests which have been carried out and which have been illustrated in Fig. 4 of the drawing. In said figure, Fig. 4a is a diagram of the relation between the number of oscillations in hertz and the accelerations in a prior driver's chair (dotted line) and the inventive subject matter (unbroken line) . In Fig. 4b is illustrated the corre- sponding relation to disturbances in y direction which in this case implies oscillations in the transversal direction of the vehicle, while in Fig. 4c the same relation in x direction has been illustrated, thus in the longitudinal direction of the vehicle. As also is evident from the drawing, the suggested structural embodiment of the spring system for vehicle seats and the like according to the invention provides for a simi- lar springing action also in vertical or z direction. In this case, the base plate 5 is similarly journalled freely sli- dable in vertical direction by means of a third set of guide means 11. Said guide means consist of at least two parallell vertical bearing rods lib, which with their upper ends are secured to the base plate and which are journalled in corre¬ sponding bearing bushings lla which are rigidly secured to the floor or base 6 by means; of a bed 12. Vertically through said hollow bed 12 extends from a position 13 in the centre of the bottom thereof a pressure spring 14 which only has been indicated by a dotted line. At its upper end said pres¬ sure spring 14 is secured at a position in vertical alignment with and preferably also horisontally coinciding with the mounting end 9 of the lower end of the tension spring 8. Owing to said design a still further improved springing action might be obtained which has been illustrated in Fig. 4d. Furthermore, the pr ssure spring 14 might be of any suitable known type but preferably said spring also is made as a gas-hydraulic spring, particularly provided with damping action.

Claims: C l a i m s 1. A spring system for resilient suspension of objects subjected to great disturbing forces with low frequencies, such as vehicle seats and particularly driver's seats in railway vehicles, and for accomodation of movements with at least three degrees of freedom between object and base, the object (1) by means of two sets of guide means (2, 4) ar- ranged vertically above each other being mounted freely movable substantially horisontally in two directions (x, y) at right angles to each other, c h a r a c t e r i z e d i n that the object (1) is permanently subjected to the force of a tension spring means (8) , which at one of its ends is secured to the centre (7) of the horisontal underside of the object (1) , supported by the upper set of guide means (2) , and at its other end (9) is secured to the centre of the lower set of guide means (4) , supported by the base, possibly at a downwards off-set position. 2. A system according to claim 1 and intended to accomo- date also movements with a further degree of freedom, namely in vertical direction (z), c h a r a c t e r i z e d i n that the lower set of guide means (4) in its turn by means of a third set of guide means (12) is freely movably supported in substantially vertical direction (z) under the permanent action of a pressure spring means (15) which at one end is attached to the centre (9) of the second set of guide means (4) and with its other end attached to the base (6) vertical¬ ly below the first end.

Inventors: ROVA JAN-ERIK, ROVA, JAN-ERIK
Applicants: ROVA JAN ERIK, ROVA, JAN-ERIK
Application year: 1994
Main classification: B60N2
IPC codes: B60N2, B61D33